Conditional disruption of mouse Klf5 results in defective eyelids with malformed meibomian glands, abnormal cornea and loss of conjunctival goblet cells.

Members of the Krüppel-like family of transcription factors regulate diverse developmental processes in various organs. Previously, we have demonstrated the role of Klf4 in the mouse ocular surface. Herein, we determined the role of the structurally related Klf5, using Klf5-conditional null (Klf5CN) mice derived by mating Klf5-LoxP and Le-Cre mice. Klf5 mRNA was detected as early as embryonic day 12 (E12) in the cornea, conjunctiva and eyelids, wherein its expression increased during development. Though the embryonic eye morphogenesis was unaltered in the Klf5CN mice, postnatal maturation was defective, resulting in smaller eyes with swollen eyelids that failed to separate properly. Klf5CN palpebral epidermis was hyperplastic with 7-9 layers of keratinocytes, compared with 2-3 in the wild type (WT). Klf5CN eyelid hair follicles and sebaceous glands were significantly enlarged, and the meibomian glands malformed. Klf5CN lacrimal glands displayed increased vasculature and large number of infiltrating cells. Klf5CN corneas were translucent, thicker with defective epithelial basement membrane and hypercellular stroma. Klf5CN conjunctiva lacked goblet cells, demonstrating that Klf5 is required for conjunctival goblet cell development. The number of Ki67-positive mitotic cells was more than doubled, consistent with the increased number of Klf5CN ocular surface epithelial cells. Co-ablation of Klf4 and Klf5 resulted in a more severe ocular surface phenotype compared with Klf4CN or Klf5CN, demonstrating that Klf4 and Klf5 share few if any, redundant functions. Thus, Klf5CN mice provide a useful model for investigating ocular surface pathologies involving meibomian gland dysfunction, blepharitis, corneal or conjunctival defects.